(a) Field of the Invention
The present invention relates to a microphone and a method of manufacturing the microphone and particularly, to a microphone having improved sensitivity by a structure of delaying the phase of sound input.
(b) Description of the Related Art
In general, microphones, which convert sound into an electrical signal, have been increasingly downsized, and accordingly, a microphone using an Micro Electro Mechanical System (MEMS) has been developed. Such a MEMS further resists humidity and heat, as compared with the Electret Condenser Microphone (ECMs) of the related art, and can be downsized and integrated with a signal processing circuit.
Generally, the MEMS microphone is either a capacitive MEMS microphone or a piezoelectric MEMS microphone. For example, the capacitive MEMS microphone includes a fixed membrane and a vibrating membrane, thus when a sound pressure is applied to the vibrating membrane from the outside, the gap between the fixed membrane and the vibrating membrane changes and the capacitance changes accordingly. The sound pressure is measured based on an electrical signal generated during the process.
Additionally, the piezoelectric MEMS microphone includes a vibrating membrane. When the vibrating membrane is deformed by external sound pressure, an electrical signal is generated by the piezoelectric effect and the sound pressure is measured.
The MEMS microphone is classified into a non-directional (omnidirectional) microphone and a directional microphone based on the directionality, and the directional microphone is classified into a bidirectional microphone and a unidirectional microphone. In particular, the bidirectional is configured to receive sounds from both the front and back, but attenuates sounds from sides, so it has a ribbon polar pattern for sound.
Further, the bidirectional microphone has an improved near field effect, so it is generally used by announcers at stadiums with substantial noise. Conversely, the unidirectional microphone is configured to maintain output in response to sound from the front, but offsets output for sound from the back, to improve the Signal to Noise (S/N) ratio for the sound from the front. Accordingly, the bidirectional microphone produces clear sound and is generally used for equipment for recognizing voice. However, the directional MEMS microphones are costly due to two or more digital MEMS microphones and Digital Signal Processing (DSP) chips.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.